Lighting fixture with image sensor

ABSTRACT

A lighting fixture with a control system, a light source, and an image sensor is disclosed. The image sensor is configured to capture an image in response to an image capture signal. The light source emits light in response to a drive signal. The control system provides the drive signal to control the light emitted by the light source, and when an image needs to be captured, provides the image capture signal. When capturing an image, the control system may coordinate the drive signal and the image capture signal so that the image sensor captures the image when the light source is emitting light, if light is needed or desired. The control system may control the drive signal to control the light emitted by the light source or control other lighting fixtures in the lighting network based, at least in part, on information derived from one or more captured images.

FIELD OF THE DISCLOSURE

The present disclosure relates to lighting fixtures, and in particularto lighting fixtures with an image sensor.

BACKGROUND

In recent years, a movement has gained traction to replace incandescentlight bulbs with lighting fixtures that employ more efficient lightingtechnologies as well as to replace relatively efficient fluorescentlighting fixtures with lighting technologies that produce a morepleasing, natural light. One such technology that shows tremendouspromise employs light emitting diodes (LEDs). Compared with incandescentbulbs, LED-based light fixtures are much more efficient at convertingelectrical energy into light, are longer lasting, and are also capableof producing light that is very natural. Compared with fluorescentlighting, LED-based fixtures are also very efficient, but are capable ofproducing light that is much more natural and more capable of accuratelyrendering colors. As a result, lighting fixtures that employ LEDtechnologies are replacing incandescent and fluorescent bulbs inresidential, commercial, and industrial applications.

Unlike incandescent bulbs that operate by subjecting a filament to adesired current, LED-based lighting fixtures require electronics todrive one or more LEDs. The electronics generally include a power supplyand special control circuitry to provide uniquely configured signalsthat are required to drive the one or more LEDs in a desired fashion.The presence of the control circuitry adds a potentially significantlevel of intelligence to the lighting fixtures that can be leveraged toemploy various types of lighting control. Such lighting control may bebased on various environmental conditions, such as ambient light,occupancy, temperature, and the like.

SUMMARY

In general, a lighting fixture with a control system, a light source,and an image sensor is disclosed. The image sensor is configured tocapture an image in response to an image capture signal. The lightsource emits light in response to a drive signal. The control systemprovides the drive signal to control the light emitted by the lightsource, and when an image needs to be captured, provides the imagecapture signal. When capturing an image, the control system maycoordinate the drive signal and the image capture signal so that theimage sensor captures the image when the light source is emitting light,if light is needed or desired during image capture. The control systemmay also control the drive signal to control the light emitted by thelight source or control other lighting fixtures in the lighting networkbased, at least in part, on information derived from one or morecaptured images. The captured images may be analyzed to determineoccupancy, ambient light characteristics, or a combination thereof.

In one embodiment, the light source of the lighting fixture isresponsive to a pulse-width modulated (PWM) drive signal. The duty cycleof the PWM drive signal dictates a relative dimming level of the lightsource's light output during general illumination. For each period ofthe PWM signal, the light source outputs light during an active portionof the PWM drive signal and does not output light during an inactiveportion of the PWM drive signal. When capturing an image, the controlsystem provides the image capture signal so that the image is capturedby the image sensor during the active portion of the PWM drive signal,such that the light source is outputting light while the image is beingcaptured, if light is needed or desired during image capture.

Images from the various lights may be sent to a central securitylocation for monitoring or storage. The images may represent stillimages as well as full or partial frames of a video.

Those skilled in the art will appreciate the scope of the disclosure andrealize additional aspects thereof after reading the following detaileddescription in association with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description serve to explain the principles of the disclosure.

FIG. 1 is a perspective view of a troffer-based lighting fixtureaccording to one embodiment of the disclosure.

FIG. 2 is a cross-section of the lighting fixture of FIG. 1.

FIG. 3 is a cross-section of the lighting fixture of FIG. 1 illustratinghow light emanates from the LEDs of the lighting fixture and isreflected out through lenses of the lighting fixture.

FIG. 4 illustrates a driver module and a communications moduleintegrated within an electronics housing of the lighting fixture of FIG.1.

FIG. 5 illustrates a driver module provided in an electronics housing ofthe lighting fixture of FIG. 1 and a communications module in anassociated housing coupled to the exterior of the electronics housingaccording to one embodiment of the disclosure.

FIGS. 6A and 6B respectively illustrate a communications moduleaccording to one embodiment, before and after being attached to thehousing of the lighting fixture.

FIGS. 7A and 7B illustrate an image module installed in a heatsink of alighting fixture according to one embodiment of the disclosure.

FIG. 8A illustrates an image sensor according to one embodiment of thedisclosure.

FIG. 8B is a graph of spectral sensitivity with respect to light for atypical CCD image sensor, a typical CMOS image sensor, and the humaneye.

FIG. 9 is a block diagram of a lighting system according to oneembodiment of the disclosure.

FIG. 10 is a block diagram of the electronics for a commissioning tool,according to one embodiment.

FIG. 11 is a block diagram of a communications module according to oneembodiment of the disclosure.

FIG. 12 is a cross-section of an exemplary LED according to a firstembodiment of the disclosure.

FIG. 13 is a cross-section of an exemplary LED according to a secondembodiment of the disclosure.

FIG. 14 is CIE 1976 chromaticity diagram that illustrates the colorpoints for three different LEDs and a black body locus.

FIG. 15 is a schematic of a driver module with an image sensor and anLED array according to one embodiment of the disclosure.

FIG. 16 is a timing diagram that shows the relationship of an imagecapture signal, a drive signal, and a control signal according to oneembodiment of the disclosure.

FIG. 17 is a block diagram of an image module according to oneembodiment of the disclosure.

FIG. 18 is a functional schematic of the driver module of FIG. 15.

FIG. 19 is a flow diagram that illustrates the functionality of thedriver module according to one embodiment.

FIG. 20 is a graph that plots individual LED current versus CCT foroverall light output according to one embodiment.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the disclosure andillustrate the best mode of practicing the disclosure. Upon reading thefollowing description in light of the accompanying drawings, thoseskilled in the art will understand the concepts of the disclosure andwill recognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

It will be understood that relative terms such as “front,” “forward,”“rear,” “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical”may be used herein to describe a relationship of one element, layer orregion to another element, layer or region as illustrated in thefigures. It will be understood that these terms are intended toencompass different orientations of the device in addition to theorientation depicted in the figures.

In general, a lighting fixture with control system, a light source, andan image sensor is disclosed. The image sensor is configured to capturean image in response to an image capture signal. The light source emitslight in response to a drive signal. The control circuitry provides thedrive signal to control the light emitted by the light source, and whenan image needs captured, provides the image capture signal. Whencapturing an image, the control circuitry may coordinate the drivesignal and the image capture signal so that the image sensor capturesthe image when the light source is emitting light, if light is needed ordesired during image capture. The control circuitry may also control thedrive signal to control the light emitted by the light source or controlother lighting fixtures in the lighting network based, at least in part,on information derived from one or more captured images. The capturesimages may be analyzed to determine occupancy, ambient lightcharacteristics, or a combination thereof.

In one embodiment, the light source of the lighting fixture isresponsive to a pulse-width modulated (PWM) drive signal. The duty cycleof the PWM drive signal dictates a relative dimming level of the lightsource's light output during general illumination. For each period ofthe PWM signal, the light source outputs light during an active portionof the PWM drive signal and does not output light during an inactiveportion of the PWM drive signal. When capturing an image, the controlsystem provides the image capture signal so that the image is capturedby the image sensor during the active portion of the PWM drive signalsuch that the light source is outputting light while the image is beingcaptured, if light is needed or desired during image capture.

Prior to delving into the details of the present disclosure, an overviewof an exemplary lighting fixture is provided. While the concepts of thepresent disclosure may be employed in any type of lighting system, theimmediately following description describes these concepts in atroffer-type lighting fixture, such as the lighting fixture 10illustrated in FIGS. 1-3. This particular lighting fixture issubstantially similar to the CR and CS series of troffer-type lightingfixtures that are manufactured by Cree, Inc. of Durham, N.C.

While the disclosed lighting fixture 10 employs an indirect lightingconfiguration wherein light is initially emitted upward from a lightsource and then reflected downward, direct lighting configurations mayalso take advantage of the concepts of the present disclosure. Inaddition to troffer-type lighting fixtures, the concepts of the presentdisclosure may also be employed in recessed lighting configurations,wall mount lighting configurations, outdoor lighting configurations, andthe like. Reference is made to co-pending and co-assigned U.S. patentapplication Ser. No. 13/589,899 filed Aug. 20, 2013, Ser. No. 13/649,531filed Oct. 11, 2012, and Ser. No. 13/606,713, now U.S. Pat. No.8,829,800, filed Sep. 7, 2012, the contents of which are incorporatedherein by reference in their entireties. Further, the functionality andcontrol techniques described below may be used to control differenttypes of lighting fixtures, as well as different groups of the same ordifferent types of lighting fixtures at the same time.

In general, troffer-type lighting fixtures, such as the lighting fixture10, are designed to mount in, on, or from a ceiling. In mostapplications, the troffer-type lighting fixtures are mounted into a dropceiling (not shown) of a commercial, educational, or governmentalfacility. As illustrated in FIGS. 1-3, the lighting fixture 10 includesa square or rectangular outer frame 12. In the central portion of thelighting fixture 10 are two rectangular lenses 14, which are generallytransparent, translucent, or opaque. Reflectors 16 extend from the outerframe 12 to the outer edges of the lenses 14. The lenses 14 effectivelyextend between the innermost portions of the reflectors 16 to anelongated heatsink 18, which functions to join the two inside edges ofthe lenses 14.

Turning now to FIGS. 2 and 3 in particular, the back side of theheatsink 18 provides a mounting structure for a solid-state lightsource, such as an LED array 20, which includes one or more rows ofindividual LEDs mounted on an appropriate substrate. The LEDs areoriented to primarily emit light upwards toward a concave cover 22. Thevolume bounded by the cover 22, the lenses 14, and the back of theheatsink 18 provides a mixing chamber 24. As such, light will emanateupwards from the LEDs of the LED array 20 toward the cover 22 and willbe reflected downward through the respective lenses 14, as illustratedin FIG. 3. Notably, not all light rays emitted from the LEDs willreflect directly off of the bottom of the cover 22 and back through aparticular lens 14 with a single reflection. Many of the light rays willbounce around within the mixing chamber 24 and effectively mix withother light rays, such that a desirably uniform light is emitted throughthe respective lenses 14.

Those skilled in the art will recognize that the type of lenses 14, thetype of LEDs, the shape of the cover 22, and any coating on the bottomside of the cover 22, among many other variables, will affect thequantity and quality of light emitted by the lighting fixture 10. Aswill be discussed in greater detail below, the LED array 20 may includeLEDs of different colors, wherein the light emitted from the variousLEDs mixes together to form a white light having a desiredcharacteristic, such as spectral content (color or color temperature),color rendering index (CRI), output level, and the like based on thedesign parameters for the particular embodiment, environmentalconditions, or the like.

As is apparent from FIGS. 2 and 3, the elongated fins of the heatsink 18may be visible from the bottom of the lighting fixture 10. Placing theLEDs of the LED array 20 in thermal contact along the upper side of theheatsink 18 allows any heat generated by the LEDs to be effectivelytransferred to the elongated fins on the bottom side of the heatsink 18for dissipation within the room in which the lighting fixture 10 ismounted. Again, the particular configuration of the lighting fixture 10illustrated in FIGS. 1-3 is merely one of the virtually limitlessconfigurations for lighting fixtures 10 in which the concepts of thepresent disclosure are applicable.

With continued reference to FIGS. 2 and 3, an electronics housing 26 isshown mounted at one end of the lighting fixture 10, and is used tohouse all or a portion of the control circuitry (not shown) used tocontrol the LED array 20 and interface with various sensors, such as theimage sensor 34. The image sensor 34 may be a CCD (charge-coupleddevice), CMOS (complementary metal-oxide semiconductor) or like imagesensor. The image sensor 34 is oriented in the lighting fixture 10 andconfigured to capture a field of view that roughly corresponds to anarea that is illuminated by light emitted from the lighting fixture 10.The image sensor 34 and its use are described in further detail below.The control circuitry is coupled to the LED array 20 and the imagesensor 34 through appropriate cabling 28. With reference to FIG. 4, thecontrol circuitry is provided by a driver module 30, a communicationsmodule 32, or a combination thereof.

At a high level, the driver module 30 is coupled to the LED array 20through the cabling 28 and directly drives the LEDs of the LED array 20based on information provided by the communications module 32 andinformation garnered from the image data obtained from the image sensor34. In one embodiment, the driver module 30 provides the primaryintelligence for the lighting fixture 10 and is capable of driving theLEDs of the LED array 20 in a desired fashion. The driver module 30 maybe provided on a single, integrated module or divided into two or moresub-modules depending the desires of the designer.

When the driver module 30 provides the primary intelligence for thelighting fixture 10, the communications module 32 acts primarily as acommunication interface that facilitates communications between thedriver module 30 and other lighting fixtures 10, a remote control system(not shown), or a portable handheld commissioning tool 36, which mayalso be configured to communicate with a remote control system in awired or wireless fashion.

Alternatively, the driver module 30 may be primarily configured to drivethe LEDs of the LED array 20 based simply on instructions from thecommunications module 32. In such an embodiment, the primaryintelligence of the lighting fixture 10 is provided in thecommunications module 32, which effectively becomes an overall controlmodule, with wired or wireless communication capability, for thelighting fixture 10. The lighting fixture 10 may share and exchangeimage data, instructions, and any other data with other lightingfixtures 10 in the lighting network or with remote entities. In essence,the communications module 32 facilitates the sharing of intelligence anddata among the lighting fixtures 10 and other entities, and in certainembodiments, may be the primary controller for the lighting fixture 10.

In the embodiment of FIG. 4, the communications module 32 may beimplemented on a separate printed circuit board (PCB) than the drivermodule 30. The respective PCBs of the driver module 30 and thecommunications module 32 may be configured to allow the connector of thecommunications module 32 to plug into the connector of the driver module30, wherein the communications module 32 is mechanically mounted, oraffixed, to the driver module 30 once the connector of thecommunications module 32 is plugged into the mating connector of thedriver module 30.

In other embodiments, a cable may be used to connect the respectiveconnectors of the driver module 30 and the communications module 32,other attachment mechanisms may be used to physically couple thecommunications module 32 to the driver module 30, or the driver module30 and the communications module 32 may be separately affixed to theinside of the electronics housing 26. In such embodiments, the interiorof the electronics housing 26 is sized appropriately to accommodate boththe driver module 30 and the communications module 32. In manyinstances, the electronics housing 26 provides a plenum rated enclosurefor both the driver module 30 and the communications module 32.

With the embodiment of FIG. 4, adding or replacing the communicationsmodule 32 requires gaining access to the interior of the electronicshousing 26. If this is undesirable, the driver module 30 may be providedalone in the electronics housing 26. The communications module 32 may bemounted outside of the electronics housing 26 in an exposed fashion orwithin a supplemental housing 38, which may be directly or indirectlycoupled to the outside of the electronics housing 26, as shown in FIG.5. The supplemental housing 38 may be bolted to the electronics housing26. The supplemental housing 38 may alternatively be connected to theelectronics housing using snap-fit or hook-and-snap mechanisms. Thesupplemental housing 38, alone or when coupled to the exterior surfaceof the electronics housing 26, may provide a plenum rated enclosure.

In embodiments where the electronics housing 26 and the supplementalhousing 38 will be mounted within a plenum rated enclosure, thesupplemental housing 38 may not need to be plenum rated. Further, thecommunications module 32 may be directly mounted to the exterior of theelectronics housing 26 without any need for a supplemental housing 38,depending on the nature of the electronics provided in thecommunications module 32, how and where the lighting fixture 10 will bemounted, and the like.

The latter embodiment, wherein the communications module 32 is mountedoutside of the electronics housing 26, may prove beneficial when thecommunications module 32 facilitates wireless communications with theother lighting fixtures 10, the remote control system, or other networkor auxiliary device. In essence, the driver module 30 may be provided inthe plenum rated electronics housing 26, which may not be conducive towireless communications. The communications module 32 may be mountedoutside of the electronics housing 26 by itself or within thesupplemental housing 38 that is designed to be more conducive towireless communications. A cable may be provided between the drivermodule 30 and the communications module 32 according to a definedcommunication interface. As an alternative, which is described in detailfurther below, the driver module 30 may be equipped with a firstconnector that is accessible through the wall of the electronics housing26. The communications module 32 may have a second connector, whichmates with the first connector to facilitate communications between thedriver module 30 and the communications module 32.

The embodiments that employ mounting the communications module 32outside of the electronics housing 26 may be somewhat less costeffective, but provide significant flexibility in allowing thecommunications module 32 or other auxiliary devices to be added to thelighting fixture 10, serviced, or replaced. The supplemental housing 38for the communications module 32 may be made of a plenum rated plasticor metal, and may be configured to readily mount to the electronicshousing 26 through snaps, screws, bolts, or the like, as well as receivethe communications module 32. The communications module 32 may bemounted to the inside of the supplemental housing 38 through snap-fits,screws, twistlocks, and the like. The cabling and connectors used forconnecting the communications module 32 to the driver module 30 may takeany available form, such as with standard category 5/6 (cat 5/6) cablehaving RJ45 connectors, edge card connectors, blind mate connectorpairs, terminal blocks and individual wires, and the like. Having anexternally mounted communications module 32 relative to the electronicshousing 26 that includes the driver module 30 allows for easy fieldinstallation of different types of communications modules 32 or moduleswith other functionality for a given driver module 30.

As illustrated in FIG. 5, the communications module 32 is mounted withinthe supplemental housing 38. The supplemental housing 38 is attached tothe electronics housing 26 with bolts. As such, the communicationsmodule 32 is readily attached and removed via the illustrated bolts.Thus, a screwdriver, ratchet, or wrench, depending on the type of headfor the bolts, is required to detach or remove the communications module32 via the supplemental housing 38.

As an alternative, the communications module 32 may be configured asillustrated in FIGS. 6A and 6B. In this configuration, thecommunications module 32 may be attached to the electronics housing 26of the lighting fixture 10 in a secure fashion and may subsequently bereleased from the electronics housing 26 without the need for boltsusing available snap-lock connectors, such as illustrated in U.S. patentapplication Ser. No. 13/868,021, which was previously incorporated byreference. Notably, the rear of the communication module housingincludes a male (or female) snap-lock connector (not shown), which isconfigured to securely and releasable engage a complementary female (ormale) snap-lock connector 40 on the electronics housing 26.

FIG. 6A illustrates the communications module 32 prior to being attachedto or just after being released from the electronics housing 26 of thelighting fixture 10. One surface of the electronics housing 26 of thelighting fixture 10 includes the snap-lock connector 40, which includesa female electrical connector that is flanked by openings that extendinto the electronics housing 26 of the lighting fixture 10. The openingscorrespond in size and location to the locking members (not shown) onthe back of the communications module 32. Further, the female electricalconnector leads to or is coupled to a PCB of the electronics for thedriver module 30. In this example, the male electrical connector of thecommunications module 32 is configured to engage the female electricalconnector, which is mounted in the electronics housing 26 of thelighting fixture 10.

As the communications module 32 is snapped into place on the electronicshousing 26 of the lighting fixture 10, as illustrated in FIG. 6B, themale electrical connector of the communications module 32 will engagethe female electrical connector of the driver module 30 as the fixturelocking members of the communications module 32 engage the respectiveopenings of the locking interfaces in the electronics housing 26. Atthis point, the communications module 32 is snapped into place to theelectronics housing 26 of the lighting fixture 10, and the respectivemale and female connectors of the communications module 32 and thedriver module 30 are fully engaged.

With reference to FIGS. 7A and 7B, one embodiment of the lightingfixture 10 is illustrated where the image sensor 34 is integrated withthe heatsink 18. The image sensor 34 is shown mounted to the back (top)side of the heatsink 18 along with the LED array 20. A lens 42 oropening is provided in the heatsink 18 such that the front surface ofthe lens 42 is flush with the front surface of the heatsink 18. A pixelarray 44 of the image sensor 34 is aligned with the lens 42 such thatthe pixel array 44 is exposed to a field of view through the lens 42 inthe heatsink 18. As illustrated, a portion of the heatsink 18 iscontoured to accommodate the lens 42 and ensure that the field of viewis not obstructed. Notably, the image sensor 34 need not be mounted tothe heatsink 18. The image sensor 34 may be mounted on any part of thelighting fixture 10 that affords the pixel array 44 access to anappropriate field of view.

An exemplary CMOS-based image sensor 34 is shown in FIG. 8A. While aCMOS-based image sensor 34 is illustrated, those skilled in the art willappreciate that other types of image sensors 34, such as CCD-basedsensors, may be employed. CMOS-based image sensors 34 are particularlyuseful in lighting applications because they have a broad spectralsensitivity that overlaps that of the human eye. As illustrated in FIG.8B, the spectral sensitivity of the human eye is relatively narrow andcentered around 560 nm. The spectral sensitivity of CMOS-based imagesensors 34 is much broader, yet substantially overlaps that of the humaneye and extends toward the red and infrared (IR) end of the spectrum.The spectral sensitivity of the CCD-based image sensor 34 is relativelybroad, but does not overlap that of the human eye as well as its CMOScounterpart.

The image sensor 34 generally includes the pixel array 44, analogprocessing circuitry 46, an analog-to-digital converter (ADC) 48,digital processing circuitry 50, and sensor control circuitry 52. Inoperation, the pixel array 44 will receive an instruction to capture animage from the sensor control circuitry 52. In response, the pixel array44 will transform the light that is detected at each pixel into ananalog signal and pass the analog signals for each pixel of the pixelarray 44 to the analog processing circuitry 46. The analog processingcircuitry 46 will filter and amplify the analog signals to createamplified signals, which are converted to digital signals by the ADC 48.The digital signals are processed by the digital processing circuitry 50to create image data for the captured image. The image data is passed tothe driver module 30 for analysis, storage, or delivery to anotherlighting fixture 10 or remote entity via the communications module 32.

The sensor control circuitry 52 will cause the pixel array 44 to capturean image in response to receiving an instruction via a sensor controlsignal (SCS) from the driver module 30 or other control entity. Thesensor control circuitry 52 controls the timing of the image processingprovided by the analog processing circuitry 46, ADC 48, and digitalprocessing circuitry 50. The sensor control circuitry 52 also sets theimage sensor's processing parameters, such as the gain and nature offiltering provided by the analog processing circuitry 46 as well as thetype of image processing provided by the digital processing circuitry50. These processing parameters may be dictated by information providedby the driver module 30.

Turning now to FIG. 9, an electrical block diagram of a lighting fixture10 is provided according to one embodiment. Assume for purposes ofdiscussion that the driver module 30, communications module 32, and LEDarray 20 are ultimately connected to form the core electronics of thelighting fixture 10, and that the communications module 32 is configuredto bidirectionally communicate with other lighting fixtures 10, thecommissioning tool 36, or other control entity through wired or wirelesstechniques. In this embodiment, a standard communication interface and afirst, or standard, protocol are used between the driver module 30 andthe communications module 32. This standard protocol allows differentdriver modules 30 to communicate with and be controlled by differentcommunications modules 32, assuming that both the driver module 30 andthe communications module 32 are operating according to the standardprotocol used by the standard communication interface. The term“standard protocol” is defined to mean any type of known or futuredeveloped, proprietary, or industry-standardized protocol.

In the illustrated embodiment, the driver module 30 and thecommunications module 32 are coupled via communication and power buses,which may be separate or integrated with one another. The communicationbus allows the communications module 32 to receive information from thedriver module 30 as well as control the driver module 30. An exemplarycommunication bus is the well-known inter-integrated circuitry (I²C)bus, which is a serial bus and is typically implemented with a two-wireinterface employing data and clock lines. Other available buses include:serial peripheral interface (SPI) bus, Dallas SemiconductorCorporation's 1-Wire serial bus, universal serial bus (USB), RS-232,Microchip Technology Incorporated's UNI/O®, and the like.

In certain embodiments, the driver module 30 includes sufficientelectronics to process an alternating current (AC) input signal (AC IN)and provide an appropriate rectified or direct current (DC) signalsufficient to power the communications module 32, and perhaps the LEDarray 20. As such, the communications module 32 does not requireseparate AC-to-DC conversion circuitry to power the electronics residingtherein, and can simply receive DC power from the driver module 30 overthe power bus. Similarly, the image sensor 34 may receive power directlyfrom the driver module 30 or via the power bus, which is powered by thedriver module 30 or other source. The image sensor 34 may also becoupled to a power source (not shown) independently of the driver andcommunications modules 30, 32.

In one embodiment, one aspect of the standard communication interface isthe definition of a standard power delivery system. For example, thepower bus may be set to a low voltage level, such as 5 volts, 12 volts,24 volts, or the like. The driver module 30 is configured to process theAC input signal to provide the defined low voltage level and providethat voltage over the power bus, thus the communications module 32 orauxiliary devices, such as the image sensor 34, may be designed inanticipation of the desired low voltage level being provided over thepower bus by the driver module 30 without concern for connecting to orprocessing an AC signal to a DC power signal for powering theelectronics of the communications module 32 or the image sensor 34.

With reference to FIG. 10, electronics for the commissioning tool 36 mayinclude control circuitry 54 that is associated with a communicationinterface 56, a user interface 58, a light projection system 60, alocation detection system 62, and a power supply 64. The controlcircuitry 54 is based on one or more application-specific integratedcircuits, microprocessors, microcontrollers, or like hardware, which areassociated with sufficient memory to run the firmware, hardware, andsoftware necessary to impart the functionality described herein.

Everything may be powered by the power supply 64, which may include abattery and any necessary DC-DC conversion circuitry to convert thebattery voltage to the desired voltages for powering the variouselectronics. The user interface 58 may include any combination ofbuttons, keypads, displays, or touch screens that supports the displayof information to the user and the input of information by a user.

The communication interface 56 may facilitate wired or wirelesscommunications with the lighting fixtures 10 directly or indirectly viaan appropriate wireless network. The communication interface 56 may alsobe used to facilitate wireless communications with a personal computer,wireless network (WLAN), and the like. Virtually any communicationstandard may be employed to facilitate such communications, includingBluetooth, IEEE 802.11 (wireless LAN), near field, cellular, and thelike wireless communication standards. For wired communications, thecommunication interface 56 may be used to communicate with a personalcomputer, wired network (LAN), lighting fixtures 10, and the like via anappropriate cable.

The light projection system 60 may take various forms, such as a laserdiode or light emitting diode that is capable of emitting a light signalthat can be received by the lighting fixtures 10 via the image sensor34, a traditional ambient light sensor, or the like. The lightprojection system 60 may be used to transmit a focused light signal thatcan be directed at and recognized by a specific lighting fixture 10 toselect the lighting fixture 10. The selected lighting fixture 10 and thecommissioning tool 36 can then start communicating with each other viathe communication interface 56 to exchange information and allow theinstructions and data to be uploaded to the lighting fixture 10. Inother embodiments, the commissioning tool 36 may query the addresses ofthe lighting fixtures 10 and systematically instruct the lightingfixtures 10 to control their light outputs to help identify eachlighting fixture 10. Once the right lighting fixture 10 is identified,the commissioning tool 36 can begin configuring or controlling thelighting fixture 10 as desired. All of the control circuitry discussedherein for the lighting fixtures 10 and commissioning tool 36 is definedas hardware based and configured to run software, firmware, and the liketo implement the described functionality.

With reference to FIG. 11, a block diagram of one embodiment of thecommunications module 32 is illustrated. The communications module 32includes control circuitry 66 and associated memory 68, which containsthe requisite software instructions and data to facilitate operation asdescribed herein. The control circuitry 66 may be associated with acommunication interface 70, which is to be coupled to the driver module30, directly or indirectly via the communication bus. The controlcircuitry 66 may be associated with a wired communication port 72, awireless communication port 74, or both, to facilitate wired or wirelesscommunications with other lighting fixtures 10, the commissioning tool36, and remote control entities. The wireless communication port 74 mayinclude the requisite transceiver electronics to facilitate wirelesscommunications with remote entities. The wired communication port 72 maysupport universal serial (USB), Ethernet, or like interfaces.

Image data may be provided directly to the driver module 30,communication module 32, or both. For example, low resoluation imagedata for ambient light or occupancy determination may be provided to thedriver module 30 for processing. High resolution image data could besent to the communication module 32 for delivery to a security center sothat security personnel can monitor high resolution images.

The capabilities of the communications module 32 may vary greatly fromone embodiment to another. For example, the communications module 32 mayact as a simple bridge between the driver module 30 and the otherlighting fixtures 10 or remote control entities. In such an embodiment,the control circuitry 66 will primarily pass data and instructionsreceived from the other lighting fixtures 10 or remote control entitiesto the driver module 30, and vice versa. The control circuitry 66 maytranslate the instructions as necessary based on the protocols beingused to facilitate communications between the driver module 30 and thecommunications module 32 as well as between the communications module 32and the remote control entities.

In other embodiments, the control circuitry 66 plays an important rolein coordinating intelligence and sharing data among the lightingfixtures 10 as well as providing significant, if not complete, controlof the driver module 30. While the communications module 32 may be ableto control the driver module 30 by itself, the control circuitry 66 mayalso be configured to receive data and instructions from the otherlighting fixtures 10 or remote control entities and use this informationto control the driver module 30. The communications module 32 may alsoprovide instructions to other lighting fixtures 10 and remote controlentities based on the sensor data from the associated driver module 30as well as the sensor data and instructions received from the otherlighting fixtures 10 and remote control entities.

Power for the control circuitry 66, memory 68, the communicationinterface 70, and the wired and/or wireless communication ports 72 and74 may be provided over the power bus via the power port. As notedabove, the power bus may receive its power from the driver module 30,which generates the DC power signal. As such, the communications module32 may not need to be connected to AC power or include rectifier andconversion circuitry. The power port and the communication port may beseparate or may be integrated with the standard communication interface.The power port and communication port are shown separately for clarity.In one embodiment, the communication bus is a 2-wire serial bus, whereinthe connector or cabling configuration may be configured such that thecommunication bus and the power bus are provided using four wires: data,clock, power, and ground. In alternative embodiments, an internal powersupply 76, which is associated with AC power or a battery is used tosupply power.

The communications module 32 may have a status indicator, such as an LED78 to indicate the operating state of the communication module. Further,a user interface 80 may be provided to allow a user to manually interactwith the communications module 32. The user interface 80 may include aninput mechanism, an output mechanism, or both. The input mechanism mayinclude one or more of buttons, keys, keypads, touchscreens, or thelike. The output mechanism may include one more LEDs, a display, or thelike. For the purposes of this application, a button is defined toinclude a push button switch, all or part of a toggle switch, rotarydial, slider, or any other mechanical input mechanism.

A description of an exemplary embodiment of the LED array 20, drivermodule 30, and the communications module 32 follows. As noted, the LEDarray 20 includes a plurality of LEDs, such as the LEDs 82 illustratedin FIGS. 12 and 13. With reference to FIG. 12, a single LED chip 84 ismounted on a reflective cup 86 using solder or a conductive epoxy, suchthat ohmic contacts for the cathode (or anode) of the LED chip 84 areelectrically coupled to the bottom of the reflective cup 86. Thereflective cup 86 is either coupled to or integrally formed with a firstlead 88 of the LED 82. One or more bond wires 90 connect ohmic contactsfor the anode (or cathode) of the LED chip 84 to a second lead 92.

The reflective cup 86 may be filled with an encapsulant material 94 thatencapsulates the LED chip 84. The encapsulant material 94 may be clearor contain a wavelength conversion material, such as a phosphor, whichis described in greater detail below. The entire assembly isencapsulated in a clear protective resin 96, which may be molded in theshape of a lens to control the light emitted from the LED chip 84.

An alternative package for an LED 82 is illustrated in FIG. 13 whereinthe LED chip 84 is mounted on a substrate 98. In particular, the ohmiccontacts for the anode (or cathode) of the LED chip 84 are directlymounted to first contact pads 100 on the surface of the substrate 98.The ohmic contacts for the cathode (or anode) of the LED chip 84 areconnected to second contact pads 102, which are also on the surface ofthe substrate 98, using bond wires 104. The LED chip 84 resides in acavity of a reflector structure 105, which is formed from a reflectivematerial and functions to reflect light emitted from the LED chip 84through the opening formed by the reflector structure 105. The cavityformed by the reflector structure 105 may be filled with an encapsulantmaterial 94 that encapsulates the LED chip 84. The encapsulant material94 may be clear or contain a wavelength conversion material, such as aphosphor.

In either of the embodiments of FIGS. 12 and 13, if the encapsulantmaterial 94 is clear, the light emitted by the LED chip 84 passesthrough the encapsulant material 94 and the protective resin 96 withoutany substantial shift in color. As such, the light emitted from the LEDchip 84 is effectively the light emitted from the LED 82. If theencapsulant material 94 contains a wavelength conversion material,substantially all or a portion of the light emitted by the LED chip 84in a first wavelength range may be absorbed by the wavelength conversionmaterial, which will responsively emit light in a second wavelengthrange. The concentration and type of wavelength conversion material willdictate how much of the light emitted by the LED chip 84 is absorbed bythe wavelength conversion material as well as the extent of thewavelength conversion. In embodiments where some of the light emitted bythe LED chip 84 passes through the wavelength conversion materialwithout being absorbed, the light passing through the wavelengthconversion material will mix with the light emitted by the wavelengthconversion material. Thus, when a wavelength conversion material isused, the light emitted from the LED 82 is shifted in color from theactual light emitted from the LED chip 84.

For example, the LED array 20 may include a group of BSY or BSG LEDs 82as well as a group of red LEDs 82. BSY LEDs 82 include an LED chip 84that emits bluish light, and the wavelength conversion material is ayellow phosphor that absorbs the blue light and emits yellowish light.Even if some of the bluish light passes through the phosphor, theresultant mix of light emitted from the overall BSY LED 82 is yellowishlight. The yellowish light emitted from a BSY LED 82 has a color pointthat falls above the Black Body Locus (BBL) on the 1976 CIE chromaticitydiagram wherein the BBL corresponds to the various color temperatures ofwhite light.

Similarly, BSG LEDs 82 include an LED chip 84 that emits bluish light;however, the wavelength conversion material is a greenish phosphor thatabsorbs the blue light and emits greenish light. Even if some of thebluish light passes through the phosphor, the resultant mix of lightemitted from the overall BSG LED 82 is greenish light. The greenishlight emitted from a BSG LED 82 has a color point that falls above theBBL on the 1976 CIE chromaticity diagram wherein the BBL corresponds tothe various color temperatures of white light.

The red LEDs 82 generally emit reddish light at a color point on theopposite side of the BBL as the yellowish or greenish light of the BSYor BSG LEDs 82. As such, the reddish light from the red LEDs 82 may mixwith the yellowish or greenish light emitted from the BSY or BSG LEDs 82to generate white light that has a desired color temperature and fallswithin a desired proximity of the BBL. In effect, the reddish light fromthe red LEDs 82 pulls the yellowish or greenish light from the BSY orBSG LEDs 82 to a desired color point on or near the BBL. Notably, thered LEDs 82 may have LED chips 84 that natively emit reddish lightwherein no wavelength conversion material is employed. Alternatively,the LED chips 84 may be associated with a wavelength conversionmaterial, wherein the resultant light emitted from the wavelengthconversion material and any light that is emitted from the LED chips 84without being absorbed by the wavelength conversion material mixes toform the desired reddish light.

The blue LED chip 84 used to form either the BSY or BSG LEDs 82 may beformed from a gallium nitride (GaN), indium gallium nitride (InGaN),silicon carbide (SiC), zinc selenide (ZnSe), or like material system.The red LED chip 84 may be formed from an aluminum indium galliumnitride (AlInGaP), gallium phosphide (GaP), aluminum gallium arsenide(AlGaAs), or like material system. Exemplary yellow phosphors includecerium-doped yttrium aluminum garnet (YAG:Ce), yellow BOSE (Ba, O, Sr,Si, Eu) phosphors, and the like. Exemplary green phosphors include greenBOSE phosphors, Lutetium aluminum garnet (LuAg), cerium doped LuAg(LuAg:Ce), Maui M535 from Lightscape Materials, Inc. of 201 WashingtonRoad, Princeton, N.J. 08540, and the like. The above LED architectures,phosphors, and material systems are merely exemplary and are notintended to provide an exhaustive listing of architectures, phosphors,and materials systems that are applicable to the concepts disclosedherein.

The International Commission on Illumination (Commission internationalede l′éclairage, or CIE) has defined various chromaticity diagrams overthe years. The chromaticity diagrams are used to project a color spacethat represents all human perceivable colors without reference tobrightness or luminance. FIG. 14 illustrates a CIE 1976 chromaticitydiagram, which includes a portion of a Planckian locus, or black bodylocus (BBL). The BBL is a path within the color space that the color ofan incandescent black body would travel as the temperature of the blackbody changes. While the color of the incandescent body may range from anorangish-red to blue, the middle portions of the path encompass what istraditionally considered as “white light.”

Correlated Color Temperature (CCT), or color temperature, is used tocharacterize white light. CCT is measured in kelvin (K) and defined bythe Illuminating Engineering Society of North America (IESNA) as “theabsolute temperature of a blackbody whose chromaticity most nearlyresembles that of the light source.” Light output that is:

-   -   below 3200 K is a yellowish white and generally considered to be        warm (white) light;    -   between 3200 K and 4000 K is generally considered neutral        (white) light; and    -   above 4000 K is bluish-white and generally considered to be cool        (white) light.        In the following discussion, the focus is providing white light        with a desired CCT, which is generally the primary goal for        general illumination. However, the concepts discussed below        equally apply to adjusting the overall color of the light        provided by the lighting fixture 10 to colors that are not        considered white or have color points that do not fall on or        relatively close to the BBL.

The coordinates [u′, v′] are used to define color points within thecolor space of the CIE 1976 chromaticity diagram. The v′ value defines avertical position and the u′ value defines a horizontal position. As anexample, the color points for a first BSY LED 82 is about (0.1900,0.5250), a second BSY LED 82 is about (0.1700, 0.4600), and a red LED 82is about (0.4900, 0.5600). Notably, the first and second BSY LEDs 82 aresignificantly spaced apart from one another along the v′ axis. As such,the first BSY LED 82 is much higher than the second BSY LED 82 in thechromaticity diagram. For ease of reference, the higher, first BSY LED82 is referenced as the high BSY-H LED, and the lower, second BSY LED 82is referenced as the low BSY-L LED.

As such, the Δv′ for the high BSY-H LED and the low BSY-L LED is about0.065 in the illustrated example. In different embodiments, the Δv′ maybe greater than 0.025, 0.030, 0.033, 0.040 0.050, 0.060, 0.075, 0.100,0.110, and 0.120, respectively. Exemplary, but not absolute upper boundsfor Δv′ may be 0.150, 0.175, or 0.200 for any of the aforementionedlower bounds. For groups of LEDs of a particular color, the Δv′ betweentwo groups of LEDs is the difference between the average v′ values foreach group of LEDs. As such, the Δv′ between groups of LEDs of aparticular color may also be greater than 0.030, 0.033, 0.040 0.050,0.060, 0.075, 0.100, 0.110, and 0.120, respectively, with the same upperbounds as described above. Further, the variation of color points amongthe LEDs 82 within a particular group of LEDs may be limited to within aseven, five, four, three, or two-step MacAdam ellipse in certainembodiments. In general, the greater the delta v′, the larger the rangethrough which the CCT of the white light can be adjusted along the blackbody locus. The closer the white light is to the black body locus, themore closely the white light will replicate that of an incandescentradiator.

In one embodiment, the LED array 20 includes a first LED group of onlylow BSY-L LEDs, a second LED group of only high BSY-H LEDs, and a thirdLED group of only red LEDs. The currents used to drive the first,second, and third LED groups may be independently controlled such thatthe intensity of the light output from the first, second, and third LEDgroups is independently controlled. As such, the light output for thefirst, second, and third LED groups may be blended or mixed to create alight output that has an overall color point virtually anywhere within atriangle formed by the color points of the respective low BSY-L LEDs,high BSY-H LEDs, and the red LEDs. Within this triangle resides asignificant portion of the BBL, and as such, the overall color point ofthe light output may be dynamically adjusted to fall along the portionof the BBL that resides within the triangle (as well as virtuallyanywhere within the triangle).

A crosshatch pattern highlights the portion of the BBL that falls withinthe triangle. Adjusting the overall color point of the light outputalong the BBL corresponds to adjusting the CCT of the light output,which as noted above is considered white light when falling on or closeto the BBL. In one embodiment, the CCT of the overall light output maybe adjusted over a range from about 2700 K to about 5700 K. In anotherembodiment, the CCT of the overall light output may be adjusted over arange from about 3000 K to 5000 K. In yet another embodiment, the CCT ofthe overall light output may be adjusted over a range from about 2700 Kto 5000 K. In yet another embodiment, the CCT of the overall lightoutput may be adjusted over a range from about 3000 K to 4000 K. Thesevariations in CCT can be accomplished while maintaining a high colorrendering index value (CRI), such as a CRI equal to or greater than 90.

To be considered “white” light, the overall color point does not have tofall precisely on the BBL. Unless defined otherwise and for the purposesof this application only, a color point within a five-step MacAdamellipse of the BBL is defined as white light on the BBL. For tightertolerances, four, three, and two-step MacAdam ellipses may be defined.

In the illustrated embodiment, the LED array 20 may include a mixture ofred LEDs 82, high BSY-H LEDs 82, and low BSY-L LEDs 82. The drivermodule 30 for driving the LED array 20 is illustrated in FIG. 15,according to one embodiment of the disclosure. The LED array 20 may bedivided into multiple strings of series connected LEDs 82. In essence,LED string S1, which includes a number of red LEDs (RED), forms a firstgroup of LEDs 82. LED string S2, which includes a number of low BSY LEDs(BSY-L), forms a second group of LEDs 82. And, LED string S3, whichincludes a number of high BSY LEDs (BSY-H), forms a third group of LEDs82.

For clarity, the various LEDs 82 of the LED array 20 are referenced asRED, BSY-L, and BSY-H in FIG. 15 to clearly indicate which LEDs arelocated in the various LED strings S1, S2, and S3. While BSY LEDs 82 areillustrated, BSG or other phosphor-coated, wavelength converted LEDs maybe employed in analogous fashion. For example, a string of high BSG-HLEDs 82 may be combined with a string of low BSG-L LEDs 82, and viceversa. Further, a string of low BSY-H LEDs may be combined with a stringof high BSG-H LEDs, and vice versa. Non-phosphor-coated LEDs, such asnon-wavelength converted red, green, and blue LEDs, may also be employedin certain embodiments.

In general, the driver module 30 controls the drive currents i₁, i₂, andi₃, which are used to drive the respective LED strings S1, S2, and S3.The ratio of drive currents i₁, i₂, and i₃ that are provided throughrespective LED strings S1, S2, and S3 may be adjusted to effectivelycontrol the relative intensities of the reddish light emitted from thered LEDs 82 of LED string S1, the yellowish/greenish light emitted fromthe low BSY-L LEDs 82 of LED string S2, and the yellow/greenish lightemitted from the high BSY-H LEDs 82 of LED string S3. The resultantlight from each LED string S1, S2, and S3 mixes to generate an overalllight output that has a desired color, CCT, and intensity, the latter ofwhich may also be referred to a dimming level. As noted, the overalllight output may be white light that falls on or within a desiredproximity of the BBL and has a desired CCT.

The number of LED strings Sx may vary from one to many and differentcombinations of LED colors may be used in the different strings. EachLED string Sx may have LEDs 82 of the same color, variations of the samecolor, or substantially different colors. In the illustrated embodiment,each LED string S1, S2, and S3 is configured such that all of the LEDs82 that are in the string are all essentially identical in color.However, the LEDs 82 in each string may vary substantially in color orbe completely different colors in certain embodiments. In anotherembodiment, three LED strings Sx with red, green, and blue LEDs may beused, wherein each LED string Sx is dedicated to a single color. In yetanother embodiment, at least two LED strings Sx may be used, wherein thesame or different colored BSY or BSG LEDs are used in one of the LEDstrings Sx and red LEDs are used in the other of the LED strings Sx. Asingle string embodiment is also envisioned, where currents may beindividually adjusted for the LEDs of the different colors using bypasscircuits, or the like.

The driver module 30 depicted in FIG. 15 generally includes AC-DCconversion circuitry 106, control circuitry 110, and a number of currentsources, such as the illustrated DC-DC converters 112. The AC-DCconversion circuitry 106 is adapted to receive an AC power signal (ACIN), rectify the AC power signal, correct the power factor of the ACpower signal, and provide a DC output signal. The DC output signal maybe used to directly power the control circuitry 110 and any othercircuitry provided in the driver module 30, including the DC-DCconverters 112, a communication interface 114, as well as the imagesensor 34.

The DC output signal may also be provided to the power bus, which iscoupled to one or more power ports, which may be part of the standardcommunication interface. The DC output signal provided to the power busmay be used to provide power to one or more external devices that arecoupled to the power bus and separate from the driver module 30. Theseexternal devices may include the communications module 32 and any numberof auxiliary devices, such as the image sensor 34. Accordingly, theseexternal devices may rely on the driver module 30 for power and can beefficiently and cost effectively designed accordingly. The AC-DCconversion circuitry 108 of the driver module 30 is robustly designed inanticipation of being required to supply power to not only its internalcircuitry and the LED array 20, but also to supply power to theseexternal devices. Such a design greatly simplifies the power supplydesign, if not eliminating the need for a power supply, and reduces thecost for these external devices.

As illustrated, the three respective DC-DC converters 112 of the drivermodule 30 provide drive currents i₁, i₂, and i₃ for the three LEDstrings S1, S2, and S3 in response to control signals CS1, CS2, and CS3.The control signals CS1, CS2, and CS3 may be pulse width modulated (PWM)signals that effectively turn the respective DC-DC converters on duringa logic high state and off during a logic low state of each period ofthe PWM signal. In one embodiment the control signals CS1, CS2, and CS3are the product of two PWM signals.

The first PWM signal is a higher frequency PWM signal that has a dutycycle that effectively sets the DC current level through a correspondingone of LED strings S1, S2, and S3, when current is allowed to passthrough the LED strings S1, S2, and S3. The second PWM signal is a lowerfrequency signal that has a duty cycle that corresponds a desireddimming or overall output level. In essence, the higher frequency PWMsignals set the relative current levels though each LED string S1, S2,and S3 while the lower frequency PWM signal determines how long thedrive currents i₁, i₂, and i₃ are allowed to pass through the LEDstrings S1, S2, and S3 during each period of the lower frequency PWMsignal. The longer the drive currents i₁, i₂, and i₃ are allowed to flowthrough the LED strings S1, S2, and S3 during each period, the higherthe output level, and vice versa.

Given the reactive components associated with the DC-DC converters 112,the relative current levels set with the higher frequency PWM signalsmay be filtered to a relative DC current. However, this DC current isessentially pulsed on and off based on the duty cycle of the lowerfrequency PWM signal. For example, the higher frequency PWM signal mayhave a switching frequency of around 200 KHz, while the lower frequencyPWM signal may have a switching frequency of around 1 KHz. FIG. 16illustrates a control signal CS_(X), which has the higher and lowerfrequency PWM components, and a resultant drive current i_(X). Duringthe active portions, the LED array 20 will emit light. During theinactive potions, the LED array will not emit light. FIG. 16 isdescribed below in greater detail in the discussion related tocoordinating image capture periods with active portions of the currentsi_(X) (drive signal).

In certain instances, a dimming device may control the AC power signal.The AC-DC conversion circuitry 106 may be configured to detect therelative amount of dimming associated with the AC power signal andprovide a corresponding dimming signal to the control circuitry 110.Based on the dimming signal, the control circuitry 110 will adjust thedrive currents i₁, i₂, and i₃ provided to each of the LED strings S1,S2, and S3 to effectively reduce the intensity of the resultant lightemitted from the LED strings S1, S2, and S3 while maintaining thedesired CCT. As described further below, the color, CCT and dimminglevels may be initiated internally or received from the commissioningtool 36, a wall controller, or another lighting fixture 10. If receivedfrom an external device via the communications module 32, the color, CCTand/or dimming levels are delivered from the communications module 32 tothe control circuitry 110 of the driver module 30 in the form of acommand via the communication bus. The driver module 30 will respond bycontrolling the drive currents i₁, i₂, and i₃ in the desired manner toachieve the requested color, CCT and/or dimming levels.

The color, CCT, and intensity of the light emitted from the LEDs 82 maybe affected by temperature. If associated with a thermistor S_(T) orother temperature-sensing device, the control circuitry 110 can controlthe drive currents i₁, i₂, and i₃ provided to each of the LED stringsS1, S2, and S3 based on ambient temperature of the LED array 20 in aneffort to compensate for temperature effects. The control circuitry 110may also trigger image capture by and receive image data from the imagesensor 34. The image data may be processed by the control circuitry 110to make occupancy determinations, determine ambient light levels, andcontrol the drive currents i₁, i₂, and i₃ in a desired fashion based onthe occupancy conditions and ambient light levels. Each of the LEDstrings S1, S2, and S3 may have different temperature compensationadjustments, which may also be functions of the magnitude of the variousdrive currents i₁, i₂, and i₃.

The control circuitry 110 may include a central processing unit (CPU)and sufficient memory 116 to enable the control circuitry 110 tobidirectionally communicate with the communications module 32 or otherdevices over the communication bus through an appropriate communicationinterface (I/F) 114 using a defined protocol, such as the standardprotocol described above. The control circuitry 110 may receive data orinstructions from the communications module 32 or other device and takeappropriate action to process the data and implement the receivedinstructions. The instructions may range from controlling how the LEDs82 of the LED array 20 are driven to returning operational data, such asimage, temperature, occupancy, light output, or ambient lightinformation, that was collected by the control circuitry 110 to thecommunications module 32 or other device via the communication bus.Notably, the functionality of the communications module 32 may beintegrated into the driver module 30, and vice versa.

Notably, when the term “control system” is used in the claims orgenerically in the specification, the term should be construed broadlyto include the hardware and any additional software or firmware that isneeded to provide the stated functionality. The term “control system”should not be construed as only software, as electronics are needed toimplement any control system that is defined herein. For example, acontrol system may, but does not necessarily, include the controlcircuitry 110, the DC-DC converters 112, the AC-DC conversion circuitry106, and the like.

For occupancy or ambient light sensing, the image sensor 34 isconfigured to capture an image in response to an image capture signalICS, which may be provided by the control circuitry 110. The imagecapture signal may be triggered on a rising edge, a falling edge, orduring an active portion of the signal. As noted, the LED array 20 emitslight in response to one or more drive signals, such as the drivecurrents i₁, i₂, i₃ that are shown driving the three LED strings S1, S2,and S3 in FIG. 15. The control circuitry 110 provides control signalsCS1, CS2, and CS3 to the respective DC-DC converters 112, which in turnprovide the drive currents i₁, i₂, i₃ that are shown driving the threeLED strings S1, S2, and S3. These drive currents i₁, i₂, i₃ areindividually and collectively referred to herein as a “drive signal,”which is used to control the light emitted by the LED array 20.

When an image needs to be captured, the control circuitry 110 providesthe image capture signal ICS. When capturing an image, the controlcircuitry 110 may coordinate the image capture signal ICS and the drivesignal (via the control signals CS1, CS2, and CS3) so that the imagesensor 34 captures the image when the LED array 20 is emitting light.The resulting image data is provided to the control circuitry 110 forfurther processing, storage, analysis, and/or distribution to otherentities, such as other lighting fixtures 10, remote entities, etc.

The control circuitry 110 may also control the drive signal to controlthe light emitted by the LED array 20 based, at least in part, oninformation derived from one or more captured images. For example, thecontrol circuitry 110 may use the image sensor 34 to facilitateoccupancy detection, ambient light sensing, or both. As such, the imagesensor 34 may replace a traditional occupancy detector, ambient lightsensor, or both. For occupancy detection, periodically captured imagesmay be analyzed by the control circuitry to determine whether someone ispresent or there is movement in a field of view that can be captured bythe image sensor 34. For example, images captured over time may beanalyzed for differences, wherein the presence of differences insuccessive images or differences between a current image and a referenceimage is indicative of occupancy. A lack of differences in thesuccessive images or between a current image and reference image may beindicative of vacancy, or a lack of occupancy. The extent or type ofdifferences required to be indicative of occupancy or vacancy may bevaried to prevent false occupancy and vacancy determinations. Further,areas of the captured image may be ignored to prevent false detections.

If the field of view for the image sensor 34 covers an area of interestand an area of no interest, the portion of the image data thatcorresponds to the area of no interest may be ignored, while only theportion of the image data that corresponds to the area of interest isanalyzed for occupancy and vacancy determinations. For example, if thefield of view for the image sensor 34 covers a conference room (an areaof interest) and extends through a window to cover an exterior sidewalk(an area of no interest), the portion of the image data that correspondsto the sidewalk or anywhere outside of the conference room may beignored, while only the portion of the image data that corresponds toconference room is analyzed for occupancy and vacancy determinations.

If the lighting fixture 10 is in an off state in which light is notbeing emitted for general illumination, the control circuitry 110 maykeep the lighting fixture 10 in the off state until occupancy (ormotion) is detected. Once occupancy is detected, the control circuitrywill transition the lighting fixture 10 to an on state in which light isemitted for general illumination at a desired output level. Afteroccupancy is no longer detected (vacancy), the control circuitry maytransition the lighting fixture 10 back to the off state. Variousoccupancy modes, or operating protocols, are known to those skilled inart.

To use the image sensor 34 for occupancy detection, images may need tobe captured when the lighting fixture 10 is in the off state or the onstate. In the off state, the lighting fixture 10 may be in anenvironment that is so dark that images captured by the image sensor 34are effectively underexposed and have insufficient information to makeoccupancy decisions. Notably, images are not captured instantly. Theimage sensor 34 captures each image during a brief image capture period.In the off state, the control circuitry 110 may cause the LED array 20to emit light for a brief period that substantially coincides with theimage capture period. As such, the field of view is illuminated duringthe image capture period by the light emitted from the LED array 20 tomake sure that the captured image is sufficiently exposed and is able toprovide sufficient information to make occupancy decisions.

When the lighting fixture 10 is in the off state, the light emitted bythe LED array 20 during an image capture period may differ from thelight emitted for general illumination during the on state in outputlevel, spectral content, or both. For example, light emitted during theimage capture period may be emitted at a lower or higher lumen levelthan the light emitted for general illumination during the on state. Thelight emitted during the image capture period may also have a differentcolor spectrum than the light emitted for general illumination duringthe on state. The different color spectrums may differ in width,location, or both. The different color spectrums may or may not overlap.For instance, the white light for general illumination may reside withina 2- or 4-step MacAdam Ellipse of the Black Body Locus (BBL) and haveCCT between 2700 and 5700 K while the light emitted during the imagecapture period may be outside of this specification and optimized forthe image sensor 34.

In one embodiment, the color spectrum for the light emitted during imagecapture is less visible or perceptible to humans than the light emittedduring general illumination. For example, the light emitted during theimage capture periods may be shifted toward red or infrared with respectto the color spectrum for the white light emitted during generalillumination. In particular, white light may be used for generalillumination, while red or infrared light may be used during the imagecapture periods. As such, the flashes of red or infrared light thatoccur during the image capture periods in darker or non-illuminatedrooms are imperceptible, or at least less perceptible and distractingthan if the white light that is emitted for general illumination wasused during the image captures periods. The image sensor 34 may have aCCD or CMOS-based sensor and be responsive to both spectrums. The lightemitted during image capture should include, but need not be limited to,light that resides in a spectrum in which the image sensor 34 isresponsive.

When the lighting fixture 10 is in the on state, the control circuitry110 will cause the LED array 20 to emit light at a desired output level,color, CCT, or a combination thereof for general illumination. Foroccupancy detection in the on state, periodically captured images may beanalyzed by the control circuitry 110 to determine whether someone ispresent or there is movement in a field of view that can be captured bythe image sensor 34. Occupancy determinations may dictate whether thelighting fixture 10 remains in the on state or transitions to the offstate in traditional fashion. The control circuitry 110 may simplycapture these images on a periodic basis while using the same whitelight that is emitted for general illumination for capturing images.

Alternatively, the control circuitry 110 may cause the LED array 20 tochange a characteristic of the light that is emitted for generalillumination during the brief image capture periods. The light emittedby the LED array 20 during the image capture periods may differ from thelight emitted for general illumination in output level or spectralcontent. For instance, light emitted during the image capture period maybe emitted at a lower or higher lumen level than the light emitted forgeneral illumination. The light emitted during the image capture periodmay also have a different color spectrum than the light emitted duringgeneral illumination. The different color spectrums may differ in width,location, or both, such that the light differs in perceptibility, color,CCT, and the like. The different color spectrums may or may not overlap.For instance, the light for general illumination may reside within a 2-or 4-step MacAdam Ellipse of the Black Body Locus (BBL) and have CCTbetween 2700 and 5700 K while the light emitted during the image captureperiod may be outside of a 4-step MacAdam Ellipse of the BBL.

Further, the output level of the light emitted during the image captureperiods may be reduced from the output level for general illumination toavoid an overexposed image when the image sensor 34 would be subjectedto too much light at the general illumination levels. In contrast, theoutput level of the light emitted during the image capture periods maybe increased from the output level for general illumination to avoid anunderexposed image when the image sensor 34 would be subjected to toolittle light at the general illumination output levels. In the on state,any changes in the characteristics of the light during the image captureperiods are preferably imperceptible or minimally perceptible to humans.The changes may be made imperceptible or minimally perceptible becausethe change in the light is for a relatively short duration thatcorresponds to the image capture period.

For lighting fixtures 10 that employ solid state lighting sources, suchas the LEDs of the LED array 20, the drive signal may be pulse widthmodulated (PWM) for at least certain output levels. Typically, the dutycycle of the PWM drive signal dictates a relative dimming level of thelight output of the LED array 20. For each period of the PWM signal, theLED array 20 outputs light during an active portion of the PWM drivesignal and does not output light during an inactive portion of the PWMdrive signal. In operation, the LED array 20 is turning on and off at afrequency that is essentially imperceptible to humans during generalillumination at some or all output levels.

Due to the phenomena of visual persistence, humans will perceive theperiodic light pulses as constant illumination. The longer that light isemitted during each PWM period, the higher the perceived output level ofthe light, and vice versa. In other words, the higher the duty cycle,the higher the perceived output level of the light, and vice versa.

While humans perceive these rapid pulses of light as constantillumination, the image sensor 34 does not. The image sensor 34 does nothave visual persistence, and image capture is affected by transitions inlight levels during image capture periods. For example, a captured imagemay be underexposed if the image is captured during an image captureperiod where the light is emitted for part of the image capture periodand not emitted for another part of the image capture period. Dependingon the light level selected for general illumination, the captured imagemay be overexposed if captured during the active portion of the PWMdrive signal when light is being emitted, and underexposed during theinactive portion of the PWM drive signal when the light is not beingemitted during general illumination.

Thus, when capturing an image, the control circuitry 110 provides theimage capture signal ICS so that the image capture period falls withinan active portion of the PWM drive signal such that the LED array 20 isemitting light during the image capture period. The control circuitry110 may also alter the characteristic of the emitted light relative tothe light emitted for general illumination during the image captureperiods. For example, the light emitted for general illumination may beprovided at a different output level, color spectrum (color, CCT, etc.),or both relative to the light emitted during the image capture periodsto help ensure proper exposure of the captured image. Alternatively, thelight emitted during the image capture periods may also have the samecharacteristics as the light emitted for general illumination. Theseconcepts apply to both the on and off states.

Images may also be captured and analyzed to determine thecharacteristics of ambient light when light is and is not being emittedfrom the lighting fixture 10. The characteristics of the ambient lightmay be used in a variety of ways. For example, the ambient lightcharacteristics may dictate the output level, color spectrum (i.e.color, CCT), or both of the light that is emitted for generalillumination, during the image capture periods, or both. As such, theimage sensor 34 may be used as an ambient light sensor. The controlcircuitry 110 can iteratively determine an actual ambient light levelduring general illumination from the captured images and regulate theoutput level of the emitted light up or down so that the actual ambientlight level corresponds to a reference output level for both generalillumination or image capture, even as light from other lightingsources, such as the sun or another lighting fixture 10 changes.

Similarly, the control circuitry 110 can iteratively determine the colorspectrum of the ambient light during general illumination from thecaptured images and regulate the color spectrum of the emitted light sothat the color spectrum of the ambient light corresponds to, or is atleast shifted in the direction of, a reference color spectrum. Thecontrol circuitry 110 can also regulate the color spectrum and level ofthe emitted light so that the ambient light color spectrum correspondsto the reference color spectrum and the ambient light level correspondsto a reference output level at the same time. When the LED array 20 isemitting light, the ambient light represents a combination of the lightemitted from the LED array 20 and any light provided by sources otherthan the lighting fixture 10.

For ambient light sensing, the images may be captured when light isbeing emitted from the LED array 20, when light is not being emittedfrom the LED array 20, or both. Images captured without light beingemitted from the LED array 20 will provide ambient light information(i.e. output level, color spectrum) without the lighting contribution ofthe LED array 20. With this information, the control circuitry 110 candetermine an output level, the color spectrum, or both for light to emitto achieve a desired reference when added to the ambient conditions.Alternatively, information from the images captured with light beingemitted from the LED array 20 allow the control circuitry 110 todetermine how to adjust the light being emitted from the LED array 20 inoutput level, color spectrum, or both to achieve a desired reference.

The images, information determined from the images, or instructionsderived from the images may be sent to other lighting fixtures 10 andremote devices. For example, a first lighting fixture 10 may receiveimages or image information from one or more other lighting fixtures 10,and use the received images or image information alone or in conjunctionwith images or image information that was captured by the first lightingfixture 10 to control the light output of the first lighting fixture 10as well as at least one of the one or more lighting fixtures 10. Assuch, the light emitted from the first lighting fixture 10 may befurther controlled based on images or image information that wasgathered from multiple lighting fixtures 10, including the firstlighting fixture 10. Images from the various lighting fixtures 10 may besent to a central security location for monitoring by security personnelor storage. As such, the same image sensor 34 may be used as an ambientlight sensor, occupancy sensor, and a security camera. The images mayrepresent still images as well as full or partial frames of a video.

The following provides some examples of the above-described conceptsusing the embodiment of FIG. 15. Assume the LED array 20 has three LEDstrings S1, S2, and S3. Each of the LED strings S1, S2, and S3 havemultiple LEDs 82. LED strings S2 and S3 only have BSY LEDs 82 with thesame or different color spectrums, while LED string S1 has only red LEDs82 with generally the same color spectrum. For general illumination, thecontrol circuitry 110 may provide the control signals CS1, CS2, and CS3to provide drive currents i₁, i₂, and i₃ through the LED strings S1, S2,and S3 at ratios that result in white light at a desired output leveland with a desired CCT. During each image capture period while providinggeneral illumination in the on state, the control circuitry 110 mayessentially turn off LED strings S2 and S3, which would normally providebluish-yellow light and continue driving LED string S1, which continuesto provide red light. As a result, the emitted light for the LED array20 is red light instead of the white light that results from mixing thebluish-yellow light from LED strings S2 and S3 with the red light fromLED string S1. Once the image capture period is over, the controlcircuitry 110 reverts to providing the control signals SC1, SC2, andSC3, which results in white light being emitted for the LED strings S1,S2, and S3 at the desired output level and with the desired CCT.

Assume the red LEDs 82 emit red light with a wavelength centered closeto 630 nm. Further assume that the image sensor 34 is responsive to redlight with wavelengths centered close to 630 nm. Since humans are notvery sensitive to light with wavelengths centered at or above 610 nm,brief flashes of red light that is centered at 630 nm is not veryperceptible to humans, especially for short periods of time, when thelighting fixture 10 is the on state during general illumination or in anoff state. In the on state, the brief periods of red light interrupt thewhite light being provided for general illumination during image captureperiods. In the off state, the LED array 20 is not outputting light forgeneral illumination. However, LED string S1 with the red LEDs will beperiodically flashed to emit red light during image capture periods inthe off state. In a darkened room, the red flashes of light when thelighting fixture 10 is in the off state will be much less perceptiblethan flashes of white light, if not essentially imperceptible. Theperceptibility will be a function of the color of the red light andlength of the image capture periods.

The image sensor 34 is able to capture images that have sufficientinformation for occupancy detection using only the red light. Notably,the output level of the red light provide by the LED string S1 duringthe image capture periods may stay the same, be increased, or bedecreased relative to output level of the red light required for generalillumination. When the drive signals are PWM signals, the image capturesignals and the drive signals are controlled such that each imagecapture period falls within an active portion of the PWM drive signalfor the LED string S1 of red LEDs 82.

In other embodiments, the control circuitry 110 may adjust one, two, orall of the drive currents i₁, i₂, and i₃ for LED strings S1, S2 and S3during the image capture periods relative to that which is used forgeneral illumination. As a result, the emitted light for the LED array20 during the image capture periods will have a different colorspectrum, output level, or both relative to the white light that is usedfor general illumination, but will use light from each of the LEDstrings S1, S2, and S3.

FIG. 16 illustrates the relationship of the control signal CS_(X), thedrive current i_(X) (drive signal), and the image capture signal ICS. Asnoted above, the control signals CS_(X) control the DC-DC converters 112to provide the PWM drive signals i_(X). When the drive signals i_(X) arePWM signals, the image capture signal ICS and the drive signals i_(X)are controlled such that each image capture period falls within anactive portion of the PWM drive current i_(X) for those LED strings S1,S2, and S3 that are being used during the image capture period. Thisconcept holds true when operating in both the on and off states.Notably, the image capture signal ICS is illustrated to correspond tothe image capture period. As noted above, image capture may be triggeredin a variety of ways, and the image capture signal ICS does not need tohave an active period that corresponds to the image capture period. Theimage capture period simply starts upon being triggered and will last adefined period of time.

As indicated above, the same light that is used for general illuminationmay be used during the image capture periods for on and off states. Whenthe drive signals are PWM signals, the image capture signals and thedrive signals are controlled such that each image capture period fallswithin an active portion of the PWM drive signal for the LED strings S1,S2, and S3.

In an alternative configuration, only (or a subset of the LED strings)LED string S1 is used for capturing images, and thus, is not used forgeneral illumination. The other two LED strings S2 and S3 are only usedfor general illumination. The LED string S1 that is only used forcapturing images may have one or more LEDs 82. If multiple LEDs 82 areused in the LED string S1, the LEDs 82 may include LEDs that emit thesame or different colors of light, such that the composite of the lightemitted by the LEDs 82 of LED string S1 has a spectrum that iscompatible with the image sensor 34 and has a spectrum that differentthan that of the light used for general illumination. For example, theLEDs 82 of LED string S1 may have a mixture of red, green, and blue LEDsto make white light; a mixture of BSY and red LEDs to make white light,only red LEDs; only infrared (IR) LEDs; only white LEDs; etc. The outputlevel of the light emitted by LED string S1 can be fixed or varied asneeded based on ambient lighting conditions, which may also bedetermined using the image sensor 34.

With reference to FIG. 17, one or more lighting fixtures 10 may beassociated with a remotely located image module 118. The image module118 will include an image sensor 34 and is configured to communicatewith the lighting fixtures 10 over a wired or wireless network tofacilitate operation that is analogous to that described above. Assumingthe lighting fixtures 10 and the image module 118 are located in thesame general vicinity, such as a conference room or outdoor parking lot,the image module 118 may capture image data and send the image data tothe lighting fixtures 10 for processing. As such, the image module 118can act as an ambient light sensor, occupancy sensor, security camera,or any combination thereof for the lighting fixtures 10. The lightingfixtures 10 will individually or collectively process the image data andmake lighting decisions based on the image data. Alternatively, theimage module 118 may process the image data, make lighting decisionsbased on the image data, and send instructions to the lighting fixtures10, wherein the lighting fixtures 10 will control their light outputbased on the instructions.

The image module 118 and the associated lighting fixtures 10 maycommunicate with each other to ensure that images are captured atappropriate times. For example, the images may need to be captured whenthe lighting fixtures are:

-   -   a. in the on state;    -   b. in the off state;    -   c. emitting light that is the same as the light used for general        illumination;    -   d. emitting light that is specially configured with a desired        output level, color spectrum, or both for image capture (and        different from the general illumination light); and    -   e. emitting light during an active period when using PWM drive        signals.        The timing of image capture and the characteristics of the light        emitted during image capture may be controlled by the image        module 118, the lighting fixtures 10, or combination thereof.        The synchronization of the image capture periods at the image        modules 118 with emission of light with the desired        characteristics at the lighting fixtures 10 can be done with        various synchronization techniques, as will be appreciated by        those skilled in the art.

One method to synchronize the image capture and light is to calibratethe clocks of the image module 118 and the lighting fixtures 10. Acalibration sequence can measure the communication latency by pulsing‘on’ one lighting fixture 10 at a time and recognizing the change inlight level with the image sensor 34. In normal operation, the time ofimage capture is coordinated between the image module 118 and lightingfixtures 10 using the communication latency to synchronize the localclocks.

The image module 118 will include control circuitry 120 that has memory122 that is sufficient to hold the software and data necessary foroperation. The control circuitry 120 is associated with the image sensor34 and at least one communication interface 124 that is configured tosupport wired or wireless communications directly or indirectly throughan appropriate network (not shown) with the lighting fixtures 10.

With reference to FIG. 18, an exemplary way to control the currents i₁,i₂, and i₃, which are provided to the respective LED strings S1, S2, andS3 is illustrated, such that the color and CCT of the overall lightoutput can be finely tuned over a relatively long range and throughoutvirtually any dimming level. As noted above, the control circuitry 110generates control signals CS1, CS2, and CS3, which control the currentsi₁, i₂, and i₃. Those skilled in the art will recognize other ways tocontrol the currents i₁, i₂, and i₃.

In essence, the control circuitry 110 of the driver module 30 is loadedwith a current model in the form of one or more functions (equation) orlook up tables for each of the currents i₁, i₂, and i₃. Each currentmodel is a reference model that is a function of dimming or outputlevel, temperature, and CCT. The output of each model provides acorresponding control signal CS1, CS2, and CS3, which effectively setsthe currents i₁, i₂, and i₃ in the LED strings S1, S2, and S3. The threecurrent models are related to each other. At any given output level,temperature, and CCT, the resulting currents i₁, i₂, and i₃ cause theLED strings S1, S2, and S3 to emit light, which when combined, providesan overall light output that has a desired output level and CCT,regardless of temperature. While the three current models do not need tobe a function of each other, they are created to coordinate with oneanother to ensure that the light from each of the strings S1, S2, and S3mix with one another in a desired fashion.

With reference to FIG. 19, an exemplary process for generating thecontrol signals CS1, CS2, and CS3 is provided. Initially, assume thatthe current models are loaded in the memory 116 of the control circuitry110. Further assume that the current models are reference models for theparticular type of lighting fixture 10.

Further assume that the desired CCT is input to a color change function126, which is based on the reference models. The color change function126 selects reference control signals R1, R2, and R3 for each of thecurrents i₁, i₂, and i₃ based on the desired CCT. Next, the referencecontrol signals R1, R2, and R3 are each adjusted, if necessary, by acurrent tune function 128 based on a set of tuning offsets. The turningoffsets may be determined through a calibration process duringmanufacturing or testing and uploaded into the control circuitry 110.The tuning offset correlates to a calibration adjustment to the currentsi₁, i₂, and i₃ that should be applied to get the CCT of the overalllight output to match a reference CCT. Details about the tuning offsetsare discussed further below. In essence, the current tune function 128modifies the reference control signals R1, R2, and R3 based on thetuning offsets to provide tuned control signals T1, T2, and T3.

In a similar fashion, a temperature compensation function 130 modifiesthe tuned control signals T1, T2, and T3 based on the currenttemperature measurements to provide temperature compensated controlsignals TC1, TC2, and TC3. Since light output from the various LEDs 82may vary in intensity and color over temperature, the temperaturecompensation function 130 effectively adjusts the currents i₁, i₂, andi₃ to substantially counter the effect of these variations. Thetemperature sensor S_(T) may provide the temperature input and isgenerally located near the LED array 20.

Finally, a dimming function 132 modifies the temperature compensatedcontrol signals TC1, TC2, and TC3 based on the desired dimming (output)levels to provide the controls signals CS1, CS2, and CS3, which drivethe DC-DC converters 112 to provide the appropriate currents i₁, i₂, andi₃ to the LED strings S1, S2, and S3. Since light output from thevarious LEDs 82 may also vary in relative intensity and color overvarying current levels, the dimming function 132 helps to ensure thatthe CCT of the overall light output corresponds to the desired CCT andintensity at the selected dimming (output) levels.

A wall controller, commissioning tool 36, or other lighting fixture 10may provide the CCT setting and dimming levels. Further, the controlcircuitry 110 may be programmed to set the CCT and dimming levelsaccording to a defined schedule, state of the occupancy and ambientlight sensors S_(O) and S_(A), other outside control input, time of day,day of week, date, or any combination thereof. For example, these levelsmay be controlled based on a desired efficiency or correlated colortemperature.

These levels may be controlled based the intensity (level) and/orspectral content of the ambient light, which is measured by analyzingimage data retrieved from the image sensor 34. When controlled based onspectral content, the dimming or CCT levels may be adjusted based on theoverall intensity of the ambient light. Alternatively, the dimminglevels, color point, or CCT levels may be adjusted to either match thespectral content of the ambient light or help fill in spectral areas ofthe ambient light that are missing or attenuated. For example, if theambient light is deficient in a cooler area of the spectrum, the lightoutput may be adjusted to provide more light in that cooler area of thespectrum, such that the ambient light and light provided by the lightingfixtures 10 combine to provide a desired spectrum. CCT, dimming, orcolor levels may also be controlled based on power conditions (poweroutage, battery backup operation, etc.), or emergency conditions (firealarm, security alarm, weather warning, etc.).

As noted, the tuning offset is generally determined during manufacture,but may also be determined and loaded into the lighting fixture 10 inthe field. The tuning offset is stored in memory 116 and correlates to acalibration adjustment to the currents i₁, i₂, and i₃ that should beapplied to get the CCT of the overall light output to match a referenceCCT. With reference to FIG. 20, exemplary current curves are providedfor reference (pre-tuned) currents and tuned (post-tuned) currents i₁,i₂, and i₃ over a CCT range of about 3000 K to 5000 K. The referencecurrents represent the currents i₁, i₂, and i₃ that are expected toprovide a desired CCT in response to the reference control signals R1,R2, and R3 for the desired CCT. However, the actual CCT that is providedin response to the reference currents i₁, i₂, and i₃ may not match thedesired CCT based on variations in the electronics in the driver module30 and the LED array 20. As such, the reference currents i₁, i₂, and i₃may need to be calibrated or adjusted to ensure that the actual CCTcorresponds to the desired CCT. The tuning offset represents thedifference between the curves for the model and tuned currents i₁, i₂,and i₃.

For single-point calibration, the tuning offset may be fixed multipliersthat can be applied over the desired CCT range for the correspondingreference currents i₁, i₂, and i₃. Applying the fixed multipliersrepresents multiplying the reference currents i₁, i₂, and i₃ bycorresponding percentages. In FIG. 13, the tuning offsets for thereference currents i₁, i₂, and i₃ may be 0.96 (96%), 1.04 (104%), and1.06 (106%), respectively. As such, as reference currents i₂, and i₃increase, the tuned currents i₂, and i₃ will increase at a greater rate.As reference current i₁ increases, the tuned current i₁ will increase ata lessor rate.

For example, a single calibration may take place at 25 C and a CCT of4000 K wherein the tuning offsets are determined for each of thecurrents i₁, i₂, and i₃. The resultant tuning offsets for the currentsi₁, i₂, and i₃ at 25 C and 4000 K may be applied to the respective modelcurrent curves. The effect is to shift each current curve up or down bya fixed percentage. As such, the same tuning offsets that are needed forcurrents i₁, i₂, and i₃ at 4000 K are applied at any selected CCTbetween 3000 K and 5000 K. The tuning offsets are implemented bymultiplying the reference control signals R1, R2, and R3 by a percentagethat causes the currents i₁, i₂, and i₃ to increase or decrease. Asnoted above, the reference control signals R1, R2, and R3 are alteredwith the tuning offsets to provide the tuned control signals T1, T2, andT3. The tuned control signals T1, T2, and T3 may be dynamically adjustedto compensate for temperature and dimming (output) levels.

While the fixed percentage-based tuning offsets may be used forcalibration and manufacturing efficiency, other tuning offsets may bederived and applied. For example, the tuning offsets may be fixedmagnitude offsets that are equally applied to all currents regardless ofthe CCT value. In a more complex scenario, an offset function can bederived for each of the currents i₁, i₂, and i₃ and applied to thecontrol signals CS1, CS2, and CS3 over the CCT range. The lightingfixture 10 need not immediately change from one CCT level to another inresponse to a user or other device changing the selected CCT level. Thelighting fixture 10 may employ a fade rate, which dictates the rate ofchange for CCT when transitioning from one CCT level to another. Thefade rate may be set during manufacture, by the commissioning tool 36,wall controller, or the like. For example, the fade rate could be 500 Kper second. Assume the CCT levels for a 5% dimming level and a 100%dimming level are 3000 K and 5000 K, respectively. If the user or someevent changed the dimming level from 5% to 100%, the CCT level maytransition from 3000 K to 5000 K at a rate of 500 K per second. Thetransition in this example would take two seconds. The dimming rate mayor may not coincide with the CCT fade rate. With a fade rate, changes inthe selected CCT level may be transitioned in a gradual fashion to avoidabrupt switches from one CCT level to another.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. A lighting fixture comprising: a solid statelighting source that is responsive to a drive signal; an image sensorconfigured to capture an image during an image capture period inresponse to an image capture signal; and a control system configured to:during an on state, control the drive signal such that light for generalillumination is emitted from the solid state lighting source; during anoff state, control the drive signal such that no light for generalillumination is emitted from the solid state lighting source; and whencapturing the image: provide the image capture signal; and control thedrive signal such that light for image capture is continuously emittedfrom the solid state lighting source throughout the image captureperiod, wherein images are captured at different times throughout the onstate and the off state and the light for general illumination differsfrom the light for image capture by at least one characteristic duringthe off state.
 2. The lighting fixture of claim 1 wherein the at leastone characteristic is color, such that a color for the light for generalillumination is different than a color for the light for image capture.3. The lighting fixture of claim 2 wherein the color for the light forimage capture is shifted toward red light relative to the color for thelight for general illumination.
 4. The lighting fixture of claim 1wherein the at least one characteristic is output level such that anoutput level for the light for general illumination is different than anoutput level for the light for image capture.
 5. The lighting fixture ofclaim 1 wherein the at least one characteristic comprises: color suchthat a color for the light for general illumination is different than acolor for the light for image capture; and output level such that anoutput level for the light for general illumination is different than anoutput level for the light for image capture.
 6. The lighting fixture ofclaim 1 wherein the control system is configured to determine an ambientlight level based at least in part on information from an image that waspreviously captured by the image sensor, and control the drive signalsuch that an output level of the light for general illumination is basedat least in part on the ambient light level.
 7. The lighting fixture ofclaim 1 wherein the light for general illumination is controlled tomatch the color spectrum of ambient light.
 8. The lighting fixture ofclaim 1 wherein the light for general illumination is controlled tocompensate for spectral deficiencies of ambient light.
 9. The lightingfixture of claim 1 wherein the control system is configured to determinean ambient light color characteristic based at least in part oninformation from an image that was previously captured by the imagesensor, and control the drive signal such that a color temperature ofthe light for general illumination is based at least in part on theambient light color characteristic.
 10. The lighting fixture of claim 1wherein the control system is configured to determine an ambient lightoutput level based at least in part on information from an image thatwas previously captured by the image sensor, and control the drivesignal such that an output level of the light for image capture is basedat least in part on the ambient light output level.
 11. The lightingfixture of claim 1 wherein the control system is configured to determinean ambient light color characteristic based at least in part oninformation from an image that was previously captured by the imagesensor, and control the drive signal such that a color of the light forimage capture is based at least in part on the ambient light colorcharacteristic.
 12. The lighting fixture of claim 1 wherein the controlsystem is configured to determine an occupancy state based at least inpart on information from at least one image that was previously capturedby the image sensor and determine whether to operate in the on state orthe off state based on the occupancy state.
 13. The lighting fixture ofclaim 12 wherein when in the on state, the control system is configuredto determine an ambient light level based at least in part oninformation from at least one image that was previously captured by theimage sensor, and control the drive signal such that an output level ofthe light for general illumination is based on the ambient light level.14. The lighting fixture of claim 1 wherein the images captured by theimage sensor are used to determine an ambient light characteristic andan occupancy state, and the control system is configured to determinehow to control the drive signal based on the ambient lightcharacteristic and whether to operate in the on state or the off statebased on the occupancy state.
 15. The lighting fixture of claim 14wherein the control system is further configured to provide instructionsto other lighting fixtures via a communication interface, wherein theinstructions are based on at least one of the ambient lightcharacteristic and the occupancy state and dictate how the otherlighting fixtures control their light output.
 16. The lighting fixtureof claim 14 wherein the control system is further configured to send theimage to at least one other lighting fixture via a communicationinterface.
 17. The lighting fixture of claim 14 wherein the controlsystem is further configured to send information from the image to atleast one other lighting fixture via a communication interface.
 18. Thelighting fixture of claim 1 wherein: throughout the image captureperiod, the control system is configured to control the drive signalsuch that the drive signal is pulse width modulated where each cycle ofthe drive signal has an active portion in which the light for imagecapture is continuously emitted and an inactive portion in which thelight for image capture is not emitted; and to capture the image, thecontrol system controls at least one of the drive signal and the imagecapture signal to ensure that the image capture period falls within theactive portion, such that the light for image capture is continuouslyemitted throughout at least the image capture period.
 19. The lightingfixture of claim 1 wherein the solid state lighting source comprises aplurality of LEDs of a first color and a plurality of LEDs of a secondcolor, which is different than the first color.
 20. The lighting fixtureof claim 19 wherein the light for image capture is the first color. 21.The lighting fixture of claim 20 wherein the first color is red.
 22. Thelighting fixture of claim 21 wherein the second color is at least one ofa combination of blue light and yellow light and a combination of bluelight and green light.
 23. The lighting fixture of claim 20 wherein thelight for general illumination is formed at least in part from the firstcolor and the second color.
 24. The lighting fixture of claim 20 whereinthe first color is infrared.
 25. The lighting fixture of claim 20wherein the light for general illumination is white light.
 26. Thelighting fixture of claim 20 wherein the light for image capture iswhite light.
 27. A lighting fixture comprising: a solid state lightingsource that is responsive to a pulse width modulated drive signal,wherein each cycle of the pulse width modulated drive signal has anactive portion in which light for image capture is continuously emittedand an inactive portion in which the light for image capture is notemitted; an image sensor configured to capture an image during an imagecapture period in response to an image capture signal; and a controlsystem configured to: during an on state, control the pulse widthmodulated drive signal such that light for general illumination isemitted from the solid state lighting source; during an off state,control the pulse width modulated drive signal such that no light isemitted from the solid state lighting source; and when capturing theimage, provide the image capture signal such that the image captureperiod falls within the active portion of the pulse width modulateddrive signal.
 28. The lighting fixture of claim 27 wherein the imagecapture period takes place during the on state.
 29. The lighting fixtureof claim 27 wherein the image capture period takes place during the offstate and light for the image capture period that is separate from thelight for general illumination is emitted when the image capture periodtakes place during the off state.
 30. The lighting fixture of claim 27wherein the control system is configured to control the pulse widthmodulated drive signal such that the light for general illuminationdiffers from the light for image capture by at least one characteristic.31. The lighting fixture of claim 30 wherein the at least onecharacteristic is color, such that a color for the light for generalillumination is different than a color for the light for image capture.32. The lighting fixture of claim 30 wherein the at least onecharacteristic is output level, such that an output level for the lightfor general illumination is different than an output level for the lightfor image capture.
 33. The lighting fixture of claim 30 wherein the atleast one characteristic comprises: color, such that a color for thelight for general illumination is different than a color for the lightfor image capture; and output level, such that an output level for thelight for general illumination is different than an output level for thelight for image capture.
 34. The lighting fixture of claim 30 whereinthe control system is configured to determine an ambient light levelbased at least in part on information from an image that was previouslycaptured by the image sensor, and control the pulse width modulateddrive signal such that an output level of the light for generalillumination is based at least in part on the ambient light level. 35.The lighting fixture of claim 30 wherein the control system isconfigured to determine an ambient light color characteristic based atleast in part on information from an image that was previously capturedby the image sensor, and control the pulse width modulated drive signalsuch that a color temperature of the light for general illumination isbased at least in part on the ambient light color characteristic. 36.The lighting fixture of claim 30 wherein the control system isconfigured to determine an occupancy state based at least in part oninformation from at least one image that was previously captured by theimage sensor, and determine whether to operate in the on state or theoff state based on the occupancy state.
 37. The lighting fixture ofclaim 27 wherein images captured by the image sensor are used todetermine an ambient light characteristic and an occupancy state, andthe control system is configured to determine how to control the pulsewidth modulated drive signal based on the ambient light characteristicand whether to operate in the on state or the off state based on theoccupancy state.
 38. The lighting fixture of claim 37 wherein thecontrol system is further configured to provide instructions to otherlighting fixtures via a communication interface, wherein theinstructions are based on at least one of the ambient lightcharacteristic and the occupancy state and dictate how the otherlighting fixtures control their light output.
 39. The lighting fixtureof claim 37 wherein the control system is further configured to send theimage to at least one other lighting fixture via a communicationinterface.
 40. The lighting fixture of claim 37 wherein the controlsystem is further configured to send information from the image to atleast one other lighting fixture via a communication interface.
 41. Thelighting fixture of claim 27 wherein the solid state lighting sourcecomprises a plurality of LEDs of a first color and a plurality of LEDsof a second color, which is different than the first color.
 42. Thelighting fixture of claim 41 wherein the light for image capture is thefirst color.
 43. The lighting fixture of claim 42 wherein the firstcolor is red.
 44. The lighting fixture of claim 42 wherein the light forgeneral illumination is formed at least in part from the first color andthe second color.
 45. The lighting fixture of claim 42 wherein the firstcolor is infrared.
 46. The lighting fixture of claim 42 wherein thelight for general illumination is white light.
 47. The lighting fixtureof claim 42 wherein the light for image capture is white light.
 48. Thelighting fixture of claim 27 wherein the image sensor is a CMOS-basedimage sensor.